Because they are
not 13.8 second cars when driven right. And because you are using the worst and slowest possible scenario of automatic SS I have ever heard of, which is just wrong IMO. Let's see at a forum list of people who submitted a time for the fastest completely stock automatic 2010 SS:
Camaro Forum - 2010 Camaro 2011 Camaro / Camaro Z28 SS Forums - Camaro5.com - View Single Post - Official 1/4 Mile 2010 Camaro Fast List
Completely stock automatics, manuals removed from list
5. 8ty8ls1 - 12.97 @ 107.61 mph, (L99, A6)
6. 1stGM - 12.98 @ 107.34 mph, (L99, A6)
13. 8secpumpgas - 13.11 @ 106.38 mph, (L99, A6)
15. acatlover13 - 13.20 @ 105.99 mph, (L99, A6)
17. Matt (tunetime) - 13.25 @ 106.42 mph, (L99, A6)
19. Scottywheels - 13.28 @ 106.43 mph, (L99, A6)
22. Midnight Maro - 13.33 @ 105.52 mph, (L99, A6)
24. HDDAN - 13.38 @ 105.65 mph, (L99, A6)
25. PwrTrip - 13.41 @ 105.01 mph, (L99, A6)
26. Kaler - 13.44 @ 108.64 mph, (L99, A6)
The same thing about you and these guys is all of you know how to drag race decently. The first couple are probably in cold conditions, but the middle of the pack is a good comparison. Some guy running a 13.80 is a bad comparison, and sucks at launching. Understand what I am saying?
These are ten examples that are all faster, and look to be driven correctly, except that last guy who needs to learn to get out of the hole better. Average trap speed was 106.5, which is slightly slower than what the magazines say. Average ET is 13.2, about exactly what the magazines say.
But you did say this:
"For comparison's sake"- Here is your comparison. Put an equal driver in a stock SS automatic, and you'll lose.
If I run a 12.5@110 and beat a stock 2010 GT500 that goofs his launch and runs a 13.1@115, I don't have the faster car, I just outdrove him. Because in talented hands, that GT500 could run low 12s.
I am not trying to give you a hard time. I am showing that since you are at least somewhat experienced at drag racing, its not fair for you to compare your car to a newbie in a faster car who doesn't really know how to sixty foot it.